What does "Blocked" really mean in the Firefox developer tools Network monitoring?
The timing section of the Firefox Network Monitor documentation, "Blocked" is explained as:
Time spent in a queue waiting for a network connection.
The browser imposes a limit on the number of simultaneous connections that can be made to a single server. In Firefox this defaults to 6
Is the limit on the number connections the only limitation? Or is the browser blocked waiting to get a connection from the OS count as blocked too?
In a fresh browser, on a first connection, before any other connection is made (so the limit should not apply here), I get blocked for 195 ms.
Is this the browser waiting for the OS? Was does "Blocked" mean here?
Answer
We changed the Firefox setting (about:config) 'network.http.max-persistent-connections-per-server' to 64 and the blocks went away. We changed it back to 6. We changed our design/development method to a more 'asynchronous' loading method so as not to have a large number simultaneous connections. The blocks were mostly loading a lot of png flags for locale settings.